1. Field of the Invention
The present invention refers to a paper that disperses quickly in water. This type of paper is called “water dispersion paper” or “water-dispersible paper.”
Water dispersion papers are sometimes used for confidential documents because they can be dispersed in water for disposal. Products that take advantage of the water absorbability and property to disperse/disintegrate in water of these papers include flushable toilet papers and toilet cleaning papers. For their water absorbability, water dispersion papers are also utilized for semination sheets and other agricultural materials, as well as sanitary materials and medical materials.
2. Description of the Related Art
Water dispersion papers proposed so far include one made by mixing papermaking fibers and fiber carboxymethyl cellulose and then adding an alkali metal compound (Patent Literature 1), and one made by mixing a water-insoluble or low-water-soluble inorganic powder into papermaking fibers or carboxymethyl cellulose (Patent Literature 2). In addition to the above, a water dispersion paper made by coating a water-soluble binder onto a support made by mixing papermaking fibers and regenerated cellulose fibers (Patent Literature 3) is also proposed, among others. Other water dispersion papers being proposed include one made by blending an alkali metal salt or alkali earth metal salt of carboxymethyl cellulose into papermaking fibers (Patent Literature 4) and one made by coating a water-soluble polymer onto a base paper made by blending hydrophobic low-molecular compound into papermaking water-dispersible fibers (Patent Literature 5), and the like.
Reflecting a growing interest in environmental issues of late, returnable containers are drawing the attention. Returnable containers generally bear an adhesive label made of a press-printed or printer-printed coated paper having an adhesive layer provided on the back side. However, separating this label from the container after use requires a cumbersome cleaning process.
To ease such trouble of cleaning, an adhesive sheet that disintegrates in water is disclosed, which is made of a water-soluble or water-dispersible base material having a coating layer appropriate for each of various recording methods provided on top (Patent Literature 6). A coated paper that separates in water is also disclosed, which is made of a base material containing water-insoluble fiber carboxy alkyl cellulose and alkalization agent, with a coating layer provided on top (Patent Literature 7).